A direct current (DC) power source, such as a fuel cell or photovoltaic cell, typically produces a low voltage at a high current. While these DC power sources provide a source of power, the power can be inconsistent, varying with local operating conditions. Because many power applications require a relatively stable source of alternating current (AC) power to operate, power conversion systems have been adapted to modify the power being supplied from DC power sources. While power conversion systems have been adapted to regulate the power from DC power sources, power conversion systems have not been adapted to modify DC power sources according to instabilities in power demands, especially when the power demands change considerably for short periods of time.
For example, when a fault condition occurs in a utility power grid, the line voltage at the output of a power conversion system can drop significantly, as will the power required of the system. During these periods, sometimes referred to as low voltage ride through (LVRT) events, conventional power conversion systems have been adapted to disconnect from the grid. Once the LVRT event has passed, a conventional power conversion system can be reconnected.
Since sources of power are repeatedly coming on and off the utility power grid during these LVRT events, the continual disconnection and reconnection of conventional power conversion systems can cause relative instability. As sources of power come on and off line, the source of power available on the grid can fluctuate, causing frequency swings or even large system wide instabilities. When extensive enough, power can be disrupted to large regions, affecting large numbers of utility customers.
Thus, there is a need for a power conversion system that can withstand a LVRT event without being disconnected from the utility power grid or other load. There is a need for systems, methods, and apparatus for operating a power converter.